How to execute single step or post-build action on a docker host if Jenkins pipeline is dockerized?

Question

Suppose I have a dockerized pipeline with multiple steps. The docker container is defined in the beginning of Jenkinsfile :

pipeline {
  agent {
    docker {
      image 'gradle:latest'
    }
  }

  stages {
    // multiple steps, all executed in 'gradle' container 
  }

post {
    always {
      sh 'git whatever-command' // will not work in 'gradle' container
    }
  }
}

I would like to execute some git commands in a post-build action. The problem is that gradle image does not have git executable.

script.sh: line 1: git: command not found

How can I execute it on Docker host still using gradle container for all other build steps? Of course I do not want to explicitly specify container for each step but that specific post-post action.

Answer 1

Ok, below is my working solution with grouping multiple stages (Build and Test) in a single dockerized stage (Dockerized gradle) and single workspace reused between docker host and docker container (see reuseNode docs ):

pipeline {
  agent {
    // the code will be checked out on out of available docker hosts
    label 'docker'
  }

  stages {
    stage('Dockerized gradle') {
      agent {
        docker {
          reuseNode true // < -- the most important part
          image 'gradle:6.5.1-jdk11'
        }
      }
      stages{
        // Stages in this block will be executed inside of a gradle container
        stage('Build') {
          steps{
            script {
                sh "gradle build -x test"
            }
          }
        }
        stage('Test') {
          steps{
            script {
              sh "gradle test"
            }
          }
        }
      }
    }
    stage('Cucumber Report') {
      // this stage will be executed on docker host labeled 'docker'
      steps {
        cucumber 'build/cucumber.json'
      }
    }
  }

  post {
    always {
      sh 'git whatever-command' // this will also work outside of 'gradle' container and reuse original workspace
    }
  }
}